Cladoceran assemblage distribution in shallow alpine lakes of Sierra Nevada (Spain) and its relationship with environmental variables.

Abstract

Subfossil cladoceran assemblages were studied in surface sediments from 17 shallow alpine lakes in the Sierra Nevada (Spain) to evaluate relationships between species assemblages and environmental variables. Factors associated with the presence of Daphnia were also investigated. Chydorids predominated in the cladoceran assemblages. Redundancy analyses (RDA) revealed that the distribution of cladoceran assemblages was mainly associated with morphometric variables (extent of catchment vegetation in basin, lake depth and size, and the presence of inlets and outlets in basin). The explanatory power of chemical parameters was lower, with total nitrogen (TN) being the most influential variable. The relative abundances of Alona quadrangularis and Chydorus sphaericus showed a significant negative relationship in the lake set, suggesting the adaptation of these species to diverging lakes conditions in Sierra Nevada. More favorable conditions for species growth (warmer waters and increased input of material from the catchment in small, open-basin lakes surrounded by alpine meadows) were observed in lakes with higher abundance of A. quadrangularis than in those with higher abundance of C. sphaericus. Our results agree with those from previous paleolimnological studies in Sierra Nevada which show an abrupt increase in the relative abundance of A. quadrangularis at the expense of C. sphaericus since 1970 associated with more favorable conditions for growth as a result of climate change. Positive relationships were also observed between the relative abundance of Daphnia pulex gr. and closed, deep basins.